Fluorescent fibers and their use

ABSTRACT

The present invention relates to a cellulosic regenerated fiber which contains an incorporated luminous pigment and an incorporated color pigment and the use of these for the production of yarns, textile fabrics and an article of reflective clothing and a process for the production of these fibers. This fiber satisfies the demands of standard EN 471, standard EN 1150, standard CAN/CSA, standard ANSI/ISEA and standard BS 471 with regard to light density, the color space and fastness values.

The present invention relates to fluorescent cellulosic regenerated fibers for use in reflective clothing such as are for example described in standard EN 471, EN 1150, CAN/CSA Z96-02, ANSI/ISEA 207-2006 and BS EN 471:2003, their use for the production of yarns and textile fabrics and a process for the production of these fibers.

BACKGROUND OF THE INVENTION

EN 471 deals exclusively with the reflective effect of personal protective equipment, in particular with reflective clothing. As a rule reflective clothing comprises a fluorescent background material and a retro-reflective material. For the purpose of the present invention, a material is described as a fluorescent material in accordance with the definition in EN 471 which emits rather than absorbs rays at a longer wave length; in the text which follows the term high-visibility material is also used. The present invention refers to the fluorescent background material but not to the retro-reflective materials.

EN 1150 deals with reflective clothing for non-professional use. The difference between standard EN 1150 in comparison to standard EN 471 is the defined area of the fluorescent material in the clothing. In addition 8 different fluorescent colors are allowed in EN 1150 (in EN 471 only yellow, orange and red fluorescent colors are allowed).

The CAN/CSA Z96-02 standard is the Canadian standard for high-visibility reflective clothing. The clothing is divided into three categories depending on the application. The demands of the area of the fluorescent material and the color coordinates after radiation correspond to standard EN 471.

The American standard ANSI/ISEA 207-2006 defines the requirements for protective clothing depending on the application. I.e. the requirements for protective clothing for the police, rescue forces and construction workers are different. The clothing for these three groups differs in terms of the requirements for the high-visibility background material.

Until now high-visibility materials were made solely on the basis of synthetic fibers and in particular polyester which, however, has disadvantages with regard to the wear comfort and safety. The disadvantages of textiles of this kind reside in particular in an unpleasant skin climate and in the development of smells after wearing for longer periods due to the insufficient moisture-regulating material properties as well as in the danger typical for synthetic fibers i.e. electrostatic charging. Complex textile structures represent an alternative. In these the outer side contains the high-visibility component and the inner side mainly comprises cellulosic fibers to improve the wear comfort such as are described in WO 2006/017709. Today fibers according to the viscose process and Lyocell process are in particular known as cellulose regenerated fibers. These are used all over the world for standard applications in textile and nonwoven fields with an individual fiber titer of between 0.8 and 15 dtex.

Cellulosic regenerated fibers can indeed be dyed with fluorescent dyestuffs using the conventional bath process. But the fibers dyed in this way do not satisfy the light fastness requirements (greater than 4, measured according to ISO 105-B02). Following xenon exposure, they are considerably bleached and display a marked change in the color shade and a considerable reduction in the color intensity which for example can be depicted as a change in the coordinates of the color space.

For decades it has been known that viscose fibers can be dyed in a permanent manner by adding pigments. Corresponding fibers are available on the market. In comparison to spun-dyed synthetic fibers, it has, however, not been possible to date, to produce spun-dyed regenerated fibers which satisfy the requirements of EN 471.

SUMMARY OF THE INVENTION

Compared to the state of the art, the present invention relates to a fiber which on the one hand satisfies the requirements of protective and reflective clothing, as for example are described in EN 471 and CAN/CSA Z96-02, and which on the other hand increases the wear comfort and safety aspects of this clothing with a justifiable economic effort. It should, therefore, be possible to produce the protective and reflective clothing from a fiber of the invention without adding any other fiber types.

It is particularly important that the textiles made from the inventive fibers pass the following requirements for background materials in accordance with EN 471 (and other standards):

Minimum light density factor (standard values in accordance with CIE publication no. 15.2) and color space

Color following exposure to xenon: the sample is illuminated according to ISO 105-B02, process 3

Rub fastness dry and wet (ISO 105-A02)

Another important criterion is the light fastness of fibers according to ISO 105-B02, process 2

Moreover, the invention relates to a suitable manufacturing process available for these fibers.

DETAILED DESCRIPTION OF THE INVENTION

The invention is directed to cellulosic regenerated fibers which contain an incorporated fluorescent pigment—in the following also called the “luminous pigment” and a color pigment incorporated into the spinning dope.

In this respect for the purpose of the present invention by fluorescent pigment, in particular a fluorescent pigment is to be understood which reveals a separate color which can be discerned by the human eye in the daylight. If this were not the case, the purpose of the invention—the warning effect—would naturally not be attained. In this respect the pigments would clearly have to differ from purely optical brighteners.

Surprisingly it was found that as a result of the color pigment, a clear improvement in the light fastness of the cellulosic regenerated fibers in accordance with the invention can be obtained compared to another fiber which only contains a color pigment. This is higher than 4, measured according to ISO 105-B02.

In this respect the necessary high light density factor is attained by the fluorescent pigment. The cellulosic regenerated fibers in accordance with the invention reveal a light density factor, measured according to EN ISO 471 of more than 0.7 for yellow fibers, more than 0.4 for orange fibers and more than 0.25 for red fibers and only slightly changed color coordinates following xenon test exposure. In the same way they reveal a light density factor, measured according to CAN/CSA Z96-02 of more than 0.38 for fluorescent yellow-green fibers, more than 0.20 for fluorescent orange-red fibers and more than 0.125 for fluorescent red fibers and only a few changed color coordinates after xenon test exposure.

The fibers also satisfy the other values demanded by EN 471 and similar norms with regard to rub fastness, perspiration fastness, wash fastness, dry cleaning fastness, hypochlorite bleaching fastness and fastness to ironing.

The spun-dyed cellulosic regenerated fibers in accordance with the invention can for example be produced according to a viscose process, a modified viscose process (e.g. the Modal process, a zinc-free viscose process with al-sulphate, the polynosic process etc. . . . ) as well as according to a solvent spinning process which is produced with organic solvents such as melted aqueous amine oxides or what are known as ionic liquids. The fibers can be designated accordingly as viscose, Modal, polynosic respectively Lyocell. In the same way other alternative processes such as the Carbamat or the Cupro process are in principle possible.

Fine spinning was performed at 1.1-25, preferably 0.2-5.0 weight percentage color pigment and 0.1-22, preferably 7.0-17.0 weight percentage of luminous pigment (always in relation to cellulose).

In general the products known to the expert for the spin dyeing of corresponding fibers are suitable as color pigments. Among other things the color pigments Aquamarine Blue 3G from Messrs. Tennents Textile Colors (Cu-phthalocyanide complexes in the form of chromophores), Aquarine Yellow 10G (Messrs. Tennants Textile Colors, Monoazo dye) and Aquis Orange 0341 (Messrs. Heubach, diarylid pyrazolon dyestuff) are suitable for blue, yellow respectively orange fluorescent fibers.

The luminous pigments preferably contain amino-modified benzoguanamines as chromophore groups. For example the yellow pigment Lunar Yellow 27 and the orange pigment Blaze 5 from the RTS series of Messrs. Swada are suitable with particle diameters of 3-4 μm. These substances are sufficiently stable in spin dyeing conditions i.e. spinning solutions respectively spinning baths with a very high respectively very low pH value or of a high temperature.

Luminous pigments are basically suitable with other chromophore groups, for example sulfonamide groups, provided that they have the stabilisers named.

In the case of fluorescent fibers for non-professional use, 8 different colors are allowed such as are described in standard EN 1150. In sports textiles the polyester overdyeing fastness plays an important role for the practical application since many sports textiles are produced from a blend of viscose, Modal or Lyocell with synthetic fibers. If only fluorescent pigments are spun into the cellulosic fibers, the light fastnesses are, also according to this standard, too low. Thus the incorporation of dyestuff pigments in accordance with the invention is also necessary in this case to attain sufficient light fastnesses.

The light fastnesses of the fibers in accordance with the invention can be further improved by the addition of stabilisers. In principle there are two types of stabilisers which can be used in fluorescent fibers and the efficiency mechanism of which is different.

In this respect these are UV absorbers and radical quenchers. With the UV absorbers, the light energy is converted into heat and is then drawn off as heat. In chemical terms these substances are either organic, conjugated aromatic compounds (benzophenone, triazine, triazole and oxal-anilide) or anorganic substances (for example nano-ZnO and nano-TiO₂) which have an effect via the mechanism of light dispersion. Radical quenchers are e.g. so-called HALS products (Hindered Amine Light Stabiliser).

The cellulosic regenerated fiber can contain other additives. In one special embodiment of the invention, the cellulosic regenerated fiber is additionally equipped with a flame-resistant agent.

One preferred embodiment of the flame-resistant fiber is produced by the additional incorporation of a pigment-shaped flame-resistant agent. In particular organophosphorous compounds come into question as pigment-shaped flame-resistant agents apart from other types. For viscose for example the highly suitable and well-known 2,2′-oxybis[5,5 dimethyl-1,3,2, dioxaphosphorinan]2,2′disulfide, available under the trade name of Exolit respectively Sandoflam.

In a further preferred embodiment of the invention, the cellulosic regenerated fiber is finished in an antibacterial form. In this respect the expert can use the substances known to him.

The object of the present invention is also the use of the fiber in accordance with the invention to produce a yarn. To be able to have suitable properties for the respective application, a yarn of this kind in accordance with the invention can also contain fibers of another origin such as for example (flame-resistant) polyester, Modacryl, para- and meta-aramides, polyamidimide (Kermel®), (flame-resistant) wool, polybenzimidazole (PBI), polyimide (P840)), polyamides, (flame-resistant) polyamides, flame-resistant acrylic fibers, melamine fibers, polyphenylensulfide (PPS), polytetrafluorethylene (PTFE), glass fibers, cotton, silk, carbon fibers, oxidised thermally stable polyacrylnitrile fibers (PANOX®) and electrically conductive fibers as well as blends of these fibers. In a preferred embodiment of the invention, the blending partners can likewise have a high-visibility finish.

Likewise the object of the present invention is the use of the fiber in accordance with the invention for the production of a textile fabric. Apart from the fibers in accordance with the invention, this textile can also contain other fibers, for example (flame-resistant) polyester, Modacryl, para- and meta-aramides, polyamidimide (Kermel®), (flame-resistant) wool, polybenzimidazole (PBI), polyimide (P84®), polyamides, (flame-resistant) polyamides, flame-resistant acrylic fibers, melamine fibers, polyphenylensulfide (PPS), polytetrafluorethylene (PTFE), glass fibers, cotton, silk, carbon fibers, oxidised thermally stabilised polyacrylnitrile fibers (PANOX®) and electrically conductive fibers and blends of these fibers. In one preferred embodiment of the invention the other fibers can likewise have a high-visibility finish. The textile fabric is preferably a woven, knitted or warp knitted fabric but can basically also be a fleece (non-woven). In the event of a woven or knit fabric, the blend of the fibers in accordance with the invention is with other fibers either by blending prior to the production of yarns, the so-called intimate blend, or by the joint use of respectively pure yarns of the different fiber types when weaving, knitting or knitting is possible.

In the same way the object of the present invention is also the use of fibers in accordance with the invention for the production of reflective clothing whereby normally the above named yarns or textile fabrics are intermediate steps within the textile chain. Different designs of articles of clothing of this kind are well known to the expert and do not, therefore, have to be described in greater detail.

EXAMPLES

The invention will now be explained on the basis of examples. These are to be understood as possible forms of the embodiment of the invention. In no way is the invention to be restricted to the scope of these examples.

The color coordinates and the luminous density factor before and after xenon exposure were measured on a fiber sheet. The fiber sheets are produced in four steps: 10 g of fibers are mixed with water, then swirled in a sheet former apparatus in accordance with ISO 3688: 1999 (E) and then finally dewatered. The wet fiber sheet is then finally dried at 92° C. for 20 min. The weight per surface area of the fiber sheet obtained in this way equals 285 g/m² and the diameter is 20 cm.

Example 1

A spun-dyed viscose fiber 1.7 dtex was produced with a content of 10.5 weight percentage of luminous pigment orange (Messrs. SWADA, RTS series, Blaze 5) and 1.7 weight percentage color pigment orange Aquis Orange 0341 (Messrs. Heubach, diarylide-pyrazolon (in relation to the cellulose mass).

The luminous fibers with the incorporated color pigments and luminous pigments remain stable following xenon test exposure (table 1). The color coordinates remain within the given range. The color density factor drops slightly. The light stability is high and the color remains intact after washing. The friction fastnesses (dry and wet) comply with the values in the standard. From this we can conclude that these luminous fibers for protective textiles satisfy standard EN 471 in all categories.

Example 2 Comparison

A spun-dyed viscose fiber 1.7 dtex contains 12% luminous pigment orange (Messrs. SWADA, RTS series blaze 5) (in relation to the cellulose mass). In this case no color pigments were used.

Example 2 shows (table 1) that the luminous fibers, which only contain luminous pigment, with spun-in luminous pigments cannot satisfy standard EN 471 since the color coordinates lie outside the given range and the light density factor drops significantly following UV exposure. In table 1 the light fastnesses are also given. The measured value of 2 for the light fastness of a fiber in accordance with the state of the art of technology is, therefore, too low to satisfy the standard.

From the examples provided 1 and 2 it is, therefore, clear that the incorporation of color pigments together with the luminous pigments is necessary to use the fibers in protective clothing.

Example 3

A spun-dyed, flame-resistant viscose fiber with an individual titer of 1.7 dtex contains 21 weight percentage 2,2′-oxybis[5,5-dimethyl-1,3,2-dioxaphosphorinan]2,2′disulfide (Exolit 5060, Messrs. Clariant), 13.2% luminous pigment yellow (Lunar Yellow 27, Messrs, SWADA) and 2.6% color pigment yellow (Aquarine Yellow 10G of Messrs. Tennants Textile Colors, chromophore groups are Monoazo groups), always in relation to the cellulose. The high-visibility fibers were illuminated in the xenon test and then the color coordinates were measured before and after the exposure. The fastnesses were determined according to the test process ISO 105-B02.

The yellow flame-resistant high-visibility fibers reveal excellent results. The light density factor of the flame-resistant high-visibility fibers is extremely high (0.98) and the value remains much higher after exposure (0.81) than is demanded in the standard (0.7 for yellow fibers). The color coordinates after exposure are almost the same as before exposure which indicates a high-quality luminous fiber. All the fastness tests reveal excellent results which meet all the demands of standard EN ISO 471.

Example 4

A spun-dyed viscose fiber with an individual titer of 1.7 dtex was produced with a content of 11.0 weight percentage luminous pigment blue (Cornet blue 60, Messrs. SWADA) and 3.2 weight percentage color pigment blue (Aquarine Blue 3G, Messrs. Tennents Textile Colors, chromophore groups are Cu-phthalocyanide complexes). The fastnesses are listed in table 1.

The polyester overdyeing fastness of the blue high-visibility fibers produced in accordance with the invention for non-professional use displays very good values; the color fastness is >4 (table 1).

These results confirm that high-visibility cellulose fibers can satisfy the standard EN 1150 and are well suited for clothing for non professional use e.g. leisure sport activities.

TABLE 1 Example 1 2 3 4 Color Orange Orange Yellow, Blue FR Light density Before exposure 0.47 0.47 0.98 factor After exposure 0.41 0.31 0.81 Color coordinates X 0.565 0.537 0.400 before Exposure Y 0.377 0.417 0.528 Color coordinates X 0.520 0.423 0.398 after Exposure Y 0.384 0.427 0.488 Rub fastness dry ISO 105-A02 4 41 Wet 2 2 Light fastness ISO 105-B02 4 2 4.5 6 Wash fastness Change in color 5 5 60° C. Dyeing Viscose 5 5 ISO 105-C06 Dyeing Wool 4-5 4-5 Polyester- Change in color 5 4-5 4-5 overdyeing Dyeing Viscose 4 2-3 4-5 Dyeing Polyester 1-2 2 4-5 Perspiration Change in color 5 acidic ISO-E04 Dyeing Viscose 5 Dyeing Wool 4-5 Perspiration Change in color 5 Alkali Dyeing Viscose 5 Dyeing Wool 4-5 

1. A cellulosic regenerated fiber comprising at least one incorporated color pigment and at least one incorporated fluorescent pigment.
 2. The cellulosic regenerated fiber according to claim 1, wherein said fiber comprises 0.1-25 weight percentage color pigment in relation to the cellulose and 0.1-22 weight percentage fluorescent pigment in relation to the cellulose.
 3. The cellulosic regenerated fiber according to claim 1, wherein the fluorescent pigments comprises amino-modified benzoguanamines as a chromophore group.
 4. The cellulosic regenerated fiber according to claim 1, wherein said fiber is produced according to a process selected from the group consisting of viscose, Modal, Lyocell, Cupro or carbamate processes.
 5. The cellulosic regenerated fiber according to claim 1, wherein said fiber further comprises-at least one light stabilizer.
 6. The cellulosic regenerated fiber according to claim 1, further comprising a flame-resistant agent.
 7. The cellulosic regenerated fiber according to claim 6, wherein the flame-resistant agent is an incorporated organophosphorous compound.
 8. The cellulosic regenerated fiber according to claim 1, further comprising an antibacterial agent.
 9. A yarn comprising the fiber according to claim
 1. 10. The yarn according to claim 9, further comprising at least one fiber of another origin.
 11. The yarn according to claim 10, wherein the fibers fiber of another origin is selected from the group consisting of polyester, flame resistant polyester, Modacryl, para- and meta-aramides, polyamidimide wool, flame resistant wool, polybenzimidazole (PBI), polyimide, polyamides, flame-resistant polyamides, flame-resistant acrylic fibers, melamine fibers, polyphenylensulfide (PPS), polytetrafluorethylene (PTFE), glass fibers, cotton, silk, carbon fibers, oxidized thermally stable polyacrylnitrile fibers and electrically conductive fibers as well as blends of these fibers.
 12. A textile fabric comprising the fiber according to claim
 1. 13. The textile fabric according to claim 12, wherein the textile fabric is selected from the group consisting of a woven fabric, knitted fabric, a warp knitted fabric, and a non-woven fabric.
 14. The textile fabric according to claim 12, wherein the fabric additionally comprises at least one fiber of another origin.
 15. The textile fabric according to claim 12, wherein the fiber of another origin is selected from the group consisting of polyester, flame resistant polyester, Modacryl, para- and meta-aramides, polyamidimide wool, flame resistant wool, PBI, polyimide, polyamides, flame-resistant polyamides, flame-resistant acrylic fibers, melamine fibers, PPS, PTFE, glass fibers, cotton, silk, carbon fibers, oxidized thermally stable polyacrylnitrile fibers and electrically conductive fibers as well as blends of these fibers.
 16. An article of reflective clothing for professional and non-professional use comprising the fiber according to claim
 1. 17. The cellulosic regenerated fiber according to claim 3, wherein said fiber comprises 0.2-5 weight percentage color pigment in relation to cellulose and 7.0-17.0 weight percentage fluorescent pigment in relation to the cellulose.
 18. The cellulosic regenerated fiber according to claim 5, wherein the at least one light stabilizer is selected from the group consisting of a UV absorber, HALS light stabilizers and anorganic light stabilizers. 